Biomaterial scaffolds for tissue engineering perform three primary functions. The first is to provide a temporary function (stiffness, strength, diffusion, and permeability) in tissue defects. The second is to provide a sufficient connected porosity to enhance biofactor delivery, cell migration and regeneration of connected tissue. The third requirement is to guide tissue regeneration into an anatomic shape.
Unfortunately, the first two functions present conflicting design requirements. That is, increasing connected porosity to enhance cell migration and tissue regeneration decreases mechanical stiffness and strength. Conversely, decreasing porosity increases mechanical stiffness and strength but impedes cell migration and tissue regeneration.
Creating biomaterial scaffolds with internal porous architectures that best satisfy the need for function and connected porosity requires balancing these two competing needs. Prior art approaches to this problem can be divided into two distinct areas. The first area concerns itself with design. The second area concerns itself with fabrication.
A first design approach, tailors microstructures to match specific elastic properties. Unfortunately, this design approach fails to provide the ability to create optimal microstructures in an anatomical shape. Also, this design approach fails to provide for the simultaneous design of a scaffold material property and the design of tissue structures in the scaffold pore space. Finally, this design approach fails to allow for the design of both scaffold material and scaffold architecture.
A second design approach uses CT data to create customized bone implants that can be manufactured using solid free form fabrication techniques. Unfortunately, this design approach does not include any specific design method to create the interior of the implant. Also, this design approach does not provide for optimized scaffold architectures with exterior anatomical shapes. Finally, this approach relies upon computer aided design (CAD) techniques which are based on computational geometry entities like surfaces and splines that are not closely related to arbitrary, complex, anatomical geometries and cannot readily use the clinical imaging data that is the basis of creating an anatomically shape scaffold.
The fabrication approach uses solid free form fabrication techniques for tissue engineering scaffolds. This technique is based on the ability to directly manufacture tissue engineering scaffolds using solid free form fabrication. In addition, this technique relies upon computer assisted design or computer aided design to create the scaffold interior design and uses CT scans to provide a template for the anatomic shape.
Unfortunately, the fabrication approach does not have the capability to optimize scaffold architecture and materials to attain natural tissue properties. Also, the fabrication approach relies upon CAD techniques which rely on the use of computational geometry entities like surfaces and splines to represent geometry. Although image data can be converted into geometric data, this does not allow for the design of arbitrary complex geometry. Furthermore, CAD techniques do not allow for the combination of optimal scaffold architectures within many anatomical shapes. Finally, the fabrication approach does not allow for the creation of designs by casting.